1. Field of the Invention
The present invention relates generally to a timer for a microwave oven, and more particularly, to a timer holding a power switch to be turned on in a microwave oven when a power control shaft controlling an output power level of the microwave oven during the cooking period is set to a maximum output mode.
2. Description of the Related Art
Typically, a timer for a microwave oven is provided with a time control shaft and a power control shaft. The time control shaft is driven by a timer motor and used for setting a cooking time of the microwave oven. The power control shaft serves to control an output power level of the microwave oven by regulating an operation time of a magnetron during the cooking time.
The timer is also provided with a plurality of reduction gears coupled to the time control shaft, a timer cam, and a main power switch. The timer cam is mounted to the time control shaft and controls the main power switch to supply electric power to the microwave oven depending on a rotation of the time control shaft corresponding to the cooking time. The main power switch is selectively turned on in accordance with a rotation of the timer cam.
Further, the timer has an auxiliary power switch, a power control cam, and an actuating lever. The auxiliary power switch controls the supply of the electric power to the magnetron during the cooking time, thus controlling an output power level of the magnetron. The power control cam rotates by the timer motor and selectively turns on the auxiliary power switch depending on a power level mode of the power control shaft. The actuating lever turns on and off the auxiliary power switch while rotating by a predetermined rotating angle according to an operation of the power control cam. In this case, the timer is designed to control a contact of the actuating lever to contact the power control cam according to the power level mode of the power control shaft, thus determining an operation of the actuating lever. The auxiliary power switch is controlled by the operation of the actuating lever, thus controlling the output power level of the microwave oven.
However, the conventional timer for the microwave oven has a problem that the auxiliary power switch is unexpectedly off for a short time since the actuating lever is operated by the power control cam even when the power control shaft is set to the maximum output mode. The conventional timer has another problem that the service life time of the timer is shortened since a contact terminal of the auxiliary power switch is rapidly worn out due to frequent opening operations of the auxiliary power switch.